Developer cartridge provided with gear having protrusions for detection

ABSTRACT

A developer cartridge includes a first gear rotatable about a first axis extending in an axial direction, and a second gear rotatable in a rotation direction about a second axis extending in the axial direction. The second gear includes: an engagement portion engageable with gear teeth of the first gear; a first protrusion and a second protrusion protruding in the axial direction. The first and second protrusions extend to be spaced apart from each other in the rotation direction. The first protrusion has first end and a second end defining a first angle therebetween about the second axis. The second protrusion has a third end and a fourth end farther away from the first protrusion than the third end is in the rotation direction. The second end and the third end define a second angle therebetween about the second axis. The first angle is smaller than the second angle.

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority from Japanese Patent Application No.2016-035464 filed Feb. 26, 2016. The entire content of the priorityapplication is incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to an electro-photographic typeimage-forming apparatus.

BACKGROUND

There is known a developer cartridge provided with a gear including arib-shaped detection portion. This detection portion is engageable withan actuator provided in an image-forming apparatus to perform newproduct detection or specification detection of the developer cartridge(for example, see Japanese Patent Application Publication no.2011-203362). In this developer cartridge, the rib-shaped detectionportion is rotatable together with the gear and has a narrow end that isconfigured to press the actuator to pivotally move the actuator. Anoptical sensor is configured to detect the pivotal movement of theactuator. The optical sensor becomes ON when detecting the pivotalmovement of the actuator, while the optical sensor becomes OFF when thenarrow end of the detection portion is separated from the actuator.

Here, the optical sensor may be configured to be ON when light isreceived by a light-receiving element, and to be OFF when light is notreceived by the light-receiving element, for example. Alternatively, theoptical sensor may be configured to become ON when light is not receivedby the light-receiving element, and become OFF when light is received bythe light-receiving element. In the following description, for the sakeof convenience, a period of time during which the optical sensor is inits ON state will be referred to as “detection period” and a period oftime during which the optical sensor is in its OFF state will bereferred to as “non-detection period”.

SUMMARY

However, in the above-described configuration of the gear, since theactuator is pressed by the end of the detection portion having a narrowwidth, the period of time in which the optical sensor is in its ON state(i.e., the detection period) becomes inevitably short. As a result, highaccuracy in the detection period is hard to be expected.

In view of the foregoing, it is an object of the present disclosure toprovide a developer cartridge that can prolong the detection period.

In order to attain the above and other objects, the disclosure providesa developer cartridge including: a first gear and a second gear. Thefirst gear is configured to rotate about a first axis extending in anaxial direction and includes gear teeth. The second gear is configuredto rotate in a rotation direction about a second axis extending in theaxial direction and has a peripheral surface extending in the rotationdirection. The second gear includes: an engagement portion formed on apart of the peripheral surface and extending in the rotation direction;a first protrusion protruding in the axial direction and extending inthe rotation direction; and a second protrusion protruding in the axialdirection and extending in the rotation direction. The engagementportion is configured to engage the gear teeth. The first protrusion hasa first end and a second end opposite to each other in the rotationdirection, the second end being arranged closer to the second protrusionthan the first end is to the second protrusion. The first protrusion andthe second protrusion are configured to move together with theengagement portion. The first protrusion and the second protrusion arearranged to be spaced apart from each other in the rotation direction.The second protrusion has a third end and a fourth end opposite to eachother in the rotation direction, the fourth end being arranged fartheraway from the first protrusion than the third end is from the firstprotrusion. The first end and the second end define a first angletherebetween about the second axis. The second end and the third enddefine a second angle therebetween about the second axis. The firstangle is smaller than the second angle.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 is a perspective view of a developing cartridge (standard-type)according to an embodiment of the disclosure;

FIG. 2 is an exploded perspective view of components constituting thedeveloping cartridge (standard-type) according to the embodiment;

FIG. 3 is a side view of the developing cartridge (standard-type)according to the embodiment in which a gear cover is detached;

FIG. 4A is a perspective view of a detection gear provided at thedeveloping cartridge (standard-type) according to the embodiment asviewed from outward thereof in an axial direction;

FIG. 4B is a perspective view of the detection gear provided at thedeveloping cartridge (standard-type) according to the embodiment asviewed from inward thereof in the axial direction;

FIG. 5 is a perspective view of the gear cover as viewed from inwardthereof in the axial direction;

FIGS. 6A and 6B are views illustrating a positional relationship betweena lever and the detection gear at its first position in the developingcartridge (standard-type) according to the embodiment, wherein FIG. 6Ais a cross-sectional view taken along a plane I-I shown in FIG. 6B;

FIGS. 7A and 7B are views illustrating a state where the lever has beenlifted up to its detection position by a first protrusion of thedetection gear in the developing cartridge (standard-type) according tothe embodiment, wherein FIG. 7A is a cross-sectional view taken along aplane II-II shown in FIG. 7B;

FIGS. 8A and 8B are views illustrating a state where the lever is aboutto be disengaged from the first protrusion of the detection gear in thedeveloping cartridge (standard-type) according to the embodiment,wherein FIG. 8A is a cross-sectional view taken along a plane III-IIIshown in FIG. 8B;

FIGS. 9A and 9B are views illustrating a state where the lever islocated between the first protrusion and a second protrusion of thedetection gear in the developing cartridge (standard-type) according tothe embodiment, wherein FIG. 9A is a cross-sectional view taken along aplane IV-IV shown in FIG. 9B;

FIGS. 10A and 10B are views illustrating a state where the lever hasbeen lifted up to its detection position by the second protrusion of thedetection gear in the developing cartridge (standard-type) according tothe embodiment, wherein FIG. 10A is a cross-sectional view taken along aplane V-V shown in FIG. 10B;

FIGS. 11A and 11B are views illustrating a state where the lever islocated near a midpoint on an outer peripheral surface of the secondprotrusion of the detection gear in the developing cartridge(standard-type) according to the embodiment, wherein FIG. 11A is across-sectional view taken along a plane VI-VI shown in FIG. 11B;

FIGS. 12A and 12B are views illustrating a state where the lever isabout to be disengaged from the second protrusion of the detection gearin the developing cartridge (standard-type) according to the embodiment,wherein FIG. 12A is a cross-sectional view taken along a plane VII-VIIshown in FIG. 12B;

FIGS. 13A and 13B are views illustrating a state where the lever hasbeen disengaged from the second protrusion of the detection gear in thedeveloping cartridge (standard-type) according to the embodiment,wherein FIG. 13A is a cross-sectional view taken along a plane VIII-VIIIshown in FIG. 13B;

FIG. 14 is a view illustrating a relationship between a torsion springand a spring engagement part of the detection gear at its first positionin the developing cartridge (standard-type) according to the embodiment;

FIG. 15 is a view illustrating the relationship between the torsionspring and the spring engagement part of the detection gear at itssecond position in the developing cartridge (standard-type) according tothe embodiment;

FIG. 16 is a perspective view of a detection gear provided at adeveloping cartridge (first high-capacity-type) according to theembodiment;

FIG. 17 is a perspective view of a detection gear provided at adeveloping cartridge (second high-capacity-type) according to theembodiment;

FIG. 18 is a perspective view of a detection gear provided at adeveloping cartridge (third high-capacity-type) according to theembodiment;

FIG. 19A is a side view of the detection gear of the developingcartridge (first high-capacity-type) according to the embodiment;

FIG. 19B is a side view of the detection gear of the developingcartridge (second high-capacity-type) according to the embodiment;

FIG. 19C is a side view of the detection gear of the developingcartridge (third high-capacity-type) according to the embodiment;

FIG. 20 is a time chart illustrating differences in signals indicativeof detection period and non-detection period in the detection gears ofthe respective types of developing cartridges;

FIG. 21 is a cross-sectional view illustrating a hypothetical statewhere a tip end of the lever is get caught by the second protrusion whenthe developing cartridge (standard-type) according to the embodiment isto be detached from a drawer;

FIG. 22A is a side view of a detection gear in a developing cartridge(standard-type) according to a modification to the embodiment;

FIG. 22B is a perspective view of the detection gear in the developingcartridge (standard-type) according to the modification;

FIG. 23A is a side view of a detection gear in a developing cartridge(second high-capacity-type) according to the modification;

FIG. 23B is a perspective view of the detection gear in the developingcartridge (second high-capacity-type) according to the modification;

FIG. 24A is a side view of a detection gear in a developing cartridge(third high-capacity-type) according to the modification;

FIG. 24B is a perspective view of the detection gear in the developingcartridge (third high-capacity-type) according to the modification;

FIG. 25 is a side view explaining a relationship between the lever andthe developing cartridge (third high-capacity-type) according to themodification in its first posture;

FIG. 26 is a side view explaining a relationship between the lever andthe developing cartridge (third high-capacity-type) according to themodification in its second posture; and

FIG. 27 is a side view illustrating how the developing cartridge (thirdhigh-capacity-type) according to the modification in its second postureis detached from the drawer.

DETAILED DESCRIPTION

Hereinafter, a detailed structure of a developer cartridge 8 accordingto an embodiment of the disclosure will be described while referring toaccompanying drawings.

As illustrated in FIGS. 1 and 2, the developer cartridge 8 includes adeveloping roller 81 extending in an axial direction, a housing 100, agear cover 200, a first protrusion 301, and a second protrusion 302. Thefirst protrusion 301 and the second protrusion 302 are exposed outsidethrough the gear cover 200. Specifically, the first protrusion 301 andthe second protrusion 302 are provided at a detection gear 300 that isrotatable about a second axis CL2 extending in the axial direction.Within the housing 100 disposed are a developer accommodating portion 84that accommodates developer, an agitator 85 configured to agitate thedeveloper in the developer accommodating portion 84, and a supply roller83 configured to supply the developer to the developing roller 81.

As illustrated in FIG. 3, the first protrusion 301 includes an arcuatewall 301A, a first end A4, a second end A2, and an extension wall 301B.The arcuate wall 301A extends in a rotation direction of the detectiongear 300. The first end A1 and second end A2 constitute one end andanother end of the arcuate wall 301A in the rotation direction,respectively. The extension wall 301B extends radially inward from thefirst end A1. The arcuate wall 301A is formed in an arcuate shapecentered on the second axis CL2.

The second end A2 is located opposite the first end A1 in the rotationdirection, and is disposed closer to the second protrusion 302 than thefirst end A1 is to the second protrusion 302 in the rotation direction.The arcuate wall 301A and the extension wall 301B are disposedrespectively at positions offset from the second axis CL2.

The second protrusion 302 is disposed upstream of and in separation fromthe first protrusion 301 in the rotation direction of the detection gear300. The second protrusion 302 includes an outer circumferential wall302A, a third end A3, a fourth end A4, a first extension wall 302B and asecond extension wall 302C. The outer circumferential wall 302A extendsin the rotation direction of the detection gear 300. The third end A3constitutes one end of the outer circumferential wall 302A in therotation direction, whereas the fourth end A4 constitutes the other endof the outer circumferential wall 302A in the rotation direction. Thefirst extension wall 302B extends radially inward from the third end A3.The second extension wall 302C extends radially inward from the fourthend A4. The outer circumferential wall 302A is formed to have an arcuateshape centered on the second axis CL2. The outer circumferential wall302A defines a radius that is substantially equal to a radius of thearcuate wall 301A of the first protrusion 301.

The fourth end A4 is located opposite the third end A3 in the rotationdirection, and is disposed farther away from the first protrusion 301than the third end A3 is from the first protrusion 301 in the rotationdirection. The outer circumferential wall 302A, the first extension wall302B, and the second extension wall 302C are all disposed offset fromthe second axis CL2.

As illustrated in FIGS. 2 and 3, the housing 100 includes a first outersurface 100A, and a second outer surface (not illustrated) opposite thefirst outer surface 100A in the axial direction. On the first outersurface 100A, a gear train including the detection gear 300 is disposed.Specifically, at the first outer surface 100A, rotatably provided are acoupling 110, a developing-roller drive gear 120, a supply-roller drivegear 130, an idle gear 140, a transmission gear 400 as an example of afirst gear, and the detection gear 300 as an example of a second gear.The gear cover 200 is attached to the first outer surface 100A such thatthe coupling 110, the developing-roller drive gear 120, the supplyroller driving gear 130, the idle gear 140, the transmission gear 400,and a part of the detection gear 300 are covered with the gear cover200.

The coupling 110 includes a coupling portion 111, and a coupling gear114 rotatable with the coupling portion 111. The coupling portion 111 isconfigured to receive a driving force that is inputted from a motor (notshown) disposed in a main body of the image-forming apparatus. Thecoupling portion 111 includes a cylindrical part 112 having acylindrical shape that extends in the axial direction, and a pair ofconvex parts 113 that protrudes radially inward from an inner peripheralsurface of the cylindrical portion 112. The convex portions 113 canengage with a body-side coupling (not shown) disposed in the main bodyof the image-forming apparatus. The coupling gear 114 is formedintegrally with the coupling portion 111 to be coaxial therewith.

The developing-roller drive gear 120 is supported by a rotation shaft81A of the developing roller 81 so as to be rotatable together with thedeveloping roller 81. The developing-roller drive gear 120 is meshedwith the coupling gear 114 of the coupling 110. The supply-roller drivegear 130 is supported by a rotation shaft 83A of the supply roller 83 soas to be rotatable together with the supply roller 83. The supply-rollerdrive gear 130 is meshed with the coupling gear 114 of the coupling 110.The idle gear 140 is meshed with the coupling gear 114 and thetransmission gear 400.

The transmission gear 400 is rotatable about a first axis CL1 extendingin the axial direction. The transmission gear 400 is supported by arotation shaft 85A of the agitator 85 so as to be rotatable togetherwith the agitator 85. The transmission gear 400 integrally includes ashaft portion 430, a large-diameter gear portion 440, and asmall-diameter gear portion 450. The shaft portion 430 has asubstantially cylindrical shape centered on the first axis CL1. Gearteeth are formed on an entire circumference of the large-diameter gearportion 440 and on an entire circumference of the small-diameter gearportion 450, respectively. The large-diameter gear portion 440 has adiameter larger than a diameter of the small-diameter gear portion 450.

In the axial direction, a distance from the first outer surface 100A tothe large-diameter gear portion 440 is smaller than a distance from thefirst outer surface 100A to the small-diameter gear portion 450. Thelarge-diameter gear portion 440 meshes the idle gear 140, while thesmall-diameter gear portion 450 is meshed with the detection gear 300.

The detection gear 300 is a sector gear that can rotate as long as thedriving force is received from the transmission gear 400. When thedeveloper cartridge 8 is in a brand-new state, the detection gear 300(the first protrusion 301 and second protrusion 302) is located at afirst position shown in FIG. 6A. While the detection gear 300 receivesthe driving force from the transmission gear 400, the detection gear 300(the first protrusion 301 and second protrusion 302) moves toward asecond position shown in FIG. 13A. Once the detection gear 300 (thefirst protrusion 301 and second protrusion 302) reaches the secondposition, the detection gear 300 halts its rotation.

Specifically, as illustrated in FIG. 4A, the detection gear 300integrally includes the first protrusion 301, the second protrusion 302,a shaft portion 310, a disc-shaped portion 320, a toothless gear portion330, a projection 340, and a spring engaging portion 350 (see FIG. 4B).The shaft portion 310 has a cylindrical shape that extends in the axialdirection and that is centered on the second axis CL2. The shaft portion310 is rotatable relative to the housing 100. More specifically, asillustrated in FIG. 2, the shaft portion 310 is rotatably supported by aboss 155 protruding from the first outer surface 100A of the housing100.

As illustrated in FIG. 4A, the disc-shaped portion 320 is formed in adisc-like shape centered on the second axis CL2. The disc-shaped portion320 extends radially outward from a generally center portion of theshaft portion 310 in the axial direction. The disc-shaped portion 320has a first surface facing the housing 100 and a second surface oppositethe first surface (see FIG. 2). The first protrusion 301 and the secondprotrusion 302 protrude from the second surface of the disc-shapedportion 320. The first protrusion 301 and second protrusion 302 aretherefore rotatable together with the disc-shaped portion 320.

The toothless gear portion 330 includes a toothless portion 331 and atoothed gear portion 332. The toothless portion 331 has a peripheralsurface that forms a portion of an outer circumferential surface of thedisc-shaped portion 320. That is, the toothless portion 331 constitutespart of the outer circumferential surface of the disc-shaped portion320. The toothed gear portion 332 is arranged at the same position asthe toothless portion 331 in the axial direction. The toothed gearportion 332 includes gear teeth protruding radially outward from theouter circumferential surface of the disc-shaped portion 320. That is,the toothed gear portion 332 is provided to extend along a part of theouter circumferential surface of the disc-shaped portion 320 in therotation direction of the detection gear 300. The toothed gear portion332 is an example of an engagement portion.

The toothed gear portion 332 includes a fifth end A5 and a sixth end A6opposite to each other in the in the rotation direction. The fifth endA5 is engaged with the small-diameter gear portion 450 of thetransmission gear 400 when the developer cartridge 8 is new (see FIG.3). That is, when the detection gear 300 is in the first position, thefifth end A5 is engaged with the transmission gear 400.

The projection 340 is disposed on the outer circumferential surface ofthe disc-shaped portion 320 at a position near the sixth end A6 of thetoothed gear portion 332 in the rotation direction. In the axialdirection, the projection 340 is provided at a position closer to thesecond protrusion 302 than the sixth end A6 of the toothed gear portion332 is to the second protrusion 302. That is, in the axial direction, adistance from the projection 340 to the housing 100 is greater than adistance from the toothed gear portion 332 to the housing 100.

The projection 340 protrudes from the outer circumferential surface ofthe disc-shaped portion 320 further radially outward than the toothedgear portion 332 does. The projection 340 has an arcuate shape having apredetermined length in the rotation direction and extending along theouter circumferential surface of the disc-shaped portion 320. Theprojection 340 is configured to engage with a restricting portion 210(see FIG. 5) formed in the gear cover 200 in the rotation direction.Specifically, when the detection gear 300 is in the second position, theprojection 340 engages with the restricting portion 210 (see FIG. 15).

As illustrated in FIG. 4B, the spring engaging portion 350 is adapted tobe engaged with a torsion spring 500 (see FIG. 2) that will be describedlater. The spring engaging portion 350 protrudes from the first surfaceof the disc-shaped portion 320 facing the housing 100. In the axialdirection, the spring engaging portion 350 has a length a that is largerthan a length β of the toothed gear portion 332 (see FIG. 6B: α>β).

The spring engaging portion 350 integrally includes a first engagingportion 351, a second engaging portion 352, a third engaging portion353, a fourth engaging portion 354, a fifth engaging portion 355, asixth engaging portion 356, and a seventh engaging portion 357.

The first engaging portion 351 is a portion that engages with thetorsion spring 500 (see FIGS. 13A and 13B) when the detection gear 300(first protrusion 301 and the second protrusion 302) is located at thefirst position. The first engaging portion 351 is disposed between thesecond engaging portion 352 and the seventh engaging portion 357, and isformed to protrude further radially outward relative to the engagingportions 352 and 357. The first engaging portion 351 has a substantiallyV shape that is tapered toward outward in a radial direction of thedetection gear 300 in a cross-sectional view.

The second engaging portion 352 is an arcuate-shaped wall centered onthe second axis CL2. The second engaging portion 352 is connected to anupstream end of the first engaging portion 351 in the rotation directionof the detection gear 300. The third engaging portion 353 is formed toextend radially outward from an upstream end of the second engagingportion 352 in the rotation direction of the detection gear 300.

The fourth engaging portion 354 is an arcuate-shaped wall centered onthe second axis CL2. The fourth engaging portion 354 is formed to have aradius larger than a radius of the second engaging portion 352. Thefourth engaging portion 354 extends from a radially outer end of thethird engaging portion 353 toward upstream in the rotation direction ofthe detection gear 300. The fourth engaging portion 354 has an upstreamend that is disposed substantially opposite to the second engagingportion 352 with respect to the second axis CL2.

The seventh engaging portion 357 is an arcuate-shaped wall centered onthe second axis CL2. The seventh engaging portion 357 is formed to havea radius substantially equal to the radius of the second engagingportion 352. The seventh engaging portion 357 extends from a downstreamend of the first engaging portion 351 toward downstream in the rotationdirection of the detection gear 300.

The sixth engaging portion 356 extends radially outward from adownstream end of the seventh engaging portion 357 in the rotationdirection of the detection gear 300. The fifth engaging portion 355extends from an upstream end of the fourth engaging portion 354 to adownstream end of the sixth engaging portion 356. The fifth engagingportion 355 and the sixth engaging portion 356 define a substantiallyV-shaped convex shape that is tapered toward outward in the radialdirection in a cross-sectional view.

As illustrated in FIG. 14, the torsion spring 500 is an example of aspring and is a torsion coil spring in the embodiment. Specifically, thetorsion spring 500 includes a coil portion 501, a first arm 510, and asecond arm 520. The first arm 510 extends from the coil portion 501toward the spring engaging portion 350 of the detection gear 300. Thesecond arm 520 extends from the coil portion 501 in a directiondifferent from a direction in which the first arm 510 extends. The coilportion 501 defines a central axis parallel to the axial direction. Thefirst arm 510 has a tip end portion that is engaged with the springengaging portion 350. The second arm 520 has a tip end portion that isengages with the housing 100. The first arm 510 and the second arm 520extend to intersect each other.

Next, positions and sizes of the first protrusion 301 and secondprotrusion 302 will be described in detail with reference to FIG. 6A.

As illustrated in FIG. 6A, the second protrusion 302 has a length in therotation direction that is larger than a length of the first protrusion301 in the rotation direction. Specifically, in the first protrusion301, the first end A1 and the second end A2 define an angle θ1therebetween about the second axis CL2. This angle θ1 may be set, forexample, in a range from 15° to 21°, and more preferably from 17° to20°. In this embodiment, the first angle θ1 for the first protrusion 301is 19°. The angle θ1 is an example of a first angle.

On the other hand, in the second protrusion 302, the third end A3 andthe fourth end A4 define an angle θ2 therebetween about the second axisCL2. This angle θ2 may be 105°, for example. The angle θ2 is an exampleof a third angle.

An angle θ3 about the second axis CL2 defined between the second end A2of the first protrusion 301 and the third end A3 of the secondprotrusion 302 may range from 62° to 69°, and more preferably from 63°to 66°. In this embodiment, the third angle θ3 is 65°. The angle θ3 isan example of a second angle.

Further, a distance D1 from the first end A1 to the second end A2 maybe, for example, set in a range from 3.0 mm to 6.0 mm, and morepreferably from 3.8 mm to 4.5 mm. In this embodiment, the distance D1 is4.03 mm.

Here, assume a first direction from the fifth end A5 toward the sixthend A6 along the toothed gear portion 332, that is, a direction oppositeto the rotation direction of the detection gear 300. A length from thefifth end A5 to the second end A2 in the first direction is shorter thana length from the fifth end A5 to the third end A3 in the rotationdirection.

In the developer cartridge 8 having the above configuration, the firstprotrusion 301 and the second protrusion 302 are used for a controller(not shown) to determine whether the developer cartridge 8 is a newproduct or to specify a specification of the developer cartridge 8.Next, how new product determination and specification identificationaccording to the embodiment are performed will be described below inbrief.

It should be noted that the detection gear 300 described above isemployed for a standard-type developer cartridge 8 that can accommodatea prescribed amount of developer that is defined as a “standard” amount.

If the developer cartridge 8 is a new product, the detection gear 300 isarranged at the first position shown in FIG. 6A. The first protrusion301 and the second protrusion 302 are respectively disposed at thepositions illustrated in FIG. 6A. When the new developer cartridge 8 isattached to the main body of the image-forming apparatus, the firstprotrusion 301 and the second protrusion 302 are arranged to be spaced,by a slight gap, from a lever 10 (see FIG. 6B) disposed in the main bodyof the image-forming apparatus.

Here, in this embodiment, the main body of the image-forming apparatusis assumed to include: a box-shaped body casing having front, rear,right, and left side walls and a top wall; and a drawer slidablerelative to the casing in a horizontal direction. Further, the lever 10is assumed to be pivotably movable relative to the drawer about a thirdaxis CL3 extending in the horizontal direction (see FIG. 6B, forexample).

More specifically, the lever 10 is pivotable between a non-detectionposition illustrated in FIG. 6B and a detection position illustrated inFIG. 7B. The lever 10 is normally urged to the non-detection position bya spring (not illustrated). The lever 10 includes a pivot shaft portion11, a first arm 12 and a second arm 13. The pivot shaft portion 11 isrotatably supported by the drawer. The first arm 12 extends from thepivot shaft portion 11 toward the detection gear 300. The second arm 13extends from the pivot shaft portion 11 in a direction away from thefirst arm 12. The first arm 12 has a distal end portion 14 having awedge-like shape that is tapered toward a distal end thereof in across-section perpendicular to the axial direction.

An optical sensor disposed in the body casing is configured to detectpivotal movement of the lever 10. The optical sensor may detect pivotalmovement of the lever 10 directly, or indirectly by detecting anotherlever that can move in accordance with the pivotal movement of the lever10. In this embodiment, the lever 10 is provided at the drawer, but thelever 10 may be provided at the body casing.

Thereafter, when a printing operation is initiated and a driving forceis inputted into the developer cartridge 8, the driving force istransmitted from the transmission gear 400 to the toothed gear portion332 of the detection gear 300 as illustrated in FIG. 7A, therebyrotating the first protrusion 301 and the second protrusion 302counterclockwise in the drawing. The rotating first protrusion 301 thencomes in contact with the distal end portion 14 of the lever 10 andpresses the lever 10 in the rotation direction, and the wedge-shapeddistal end portion 14 is moved. When the moving distal end portion 14reaches an outer surface of the first protrusion 301, the distal endportion 14 is supported by the outer surface to be placed at a positioncorresponding to the detection position.

When the distal end portion 14 is pushed up to the positioncorresponding to the detection position in this way, the lever 10 pivotsto the detection position as illustrated in FIG. 7B. Accordingly, thelever 10 at the detection position can be detected by the opticalsensor. That is, in FIGS. 7A and 7B, the optical sensor has switched tothe ON state from the OFF state (FIGS. 6A and 6B). Upon detecting the ONstate of the optical sensor, the controller (not illustrated) determinesthat the developer cartridge 8 is a new product.

Thereafter, while the detection gear 300 rotates by a predeterminedrotation angle as sequentially illustrated in FIGS. 7A, 7B, 8A and 8B,the distal end portion 14 is maintained at the position corresponding tothe detection position by the arcuate wall 301A of the first protrusion301. The lever 10 is thus maintained at the detection position. Here, aperiod of time in which the lever 10 is maintained at the detectionposition (hereinafter also referred to as “detection period”) isdetermined to be a predetermined first period T1 (see FIG. 20) bysetting the first angle θ1 and the distance D1 as described above.

When the distal end portion 14 is separated from the arcuate wall 301Aof the first protrusion 301, the biasing force of the non-illustratedspring causes the lever 10 to pivot toward the non-detection position.As illustrated in FIGS. 9A and 9B, when the distal end portion 14reaches a position corresponding to the non-detection position, thelever 10 pivots to the non-detection position, and the optical sensor isswitched from the ON state to the OFF state. Specifically, while thelever 10 is pivoting from the detection position toward thenon-detection position, light emitted from a light-emitting part of theoptical sensor is gradually shielded by the lever 10 (or another lever).When the lever 10 reaches the non-detection position, the light iscompletely blocked and the optical sensor is switched into the OFFstate. That is, the optical sensor is completely becomes ON (an amountof light received is generally 100%) when the lever 10 is at thedetection position, whereas the optical sensor becomes completely OFF(the amount of light received is generally 0%) when the lever 10 is atthe non-detection position.

Thereafter, until the second protrusion 302 comes in contact with thedistal end portion 14, the distal end portion 14 is maintained at theposition corresponding to the non-detection position and the lever 10 ismaintained at the non-detection position. A period of time in which thelever 10 is maintained at the non-detection position between the firstprotrusion 301 and the second protrusion 302 (hereinafter also referredto as “non-detection period”) is substantially equal to the detectionperiod by setting the third angle θ3 as described above.

When the rotating second protrusion 302 comes in contact with the distalend portion 14 and presses the distal end portion 14 in the rotationdirection, the distal end portion 14 moves again up toward the positioncorresponding to the detection position. When the distal end portion 14again reaches the position corresponding to the detection position asillustrated in FIG. 10A and 10B, the lever 10 reaches the detectionposition and the optical sensor is switched from the OFF state to the ONstate.

Thereafter, while the distal end portion 14 is supported by the outercircumferential wall 302A of the second protrusion 302 as sequentiallyillustrated in FIGS. 11A, 11B, 12A and 12B, the lever 10 is maintainedat the detection position. Here, since the second angle θ2 is set asdescribed above, that is, since the length of the outer circumferentialwall 302A in the rotation direction is larger than the length of thearcuate wall 301A in the rotation direction, the detection period forthe second time is a second period T2 that is longer than the firstperiod T1. When the detection period for the second time is determinedto be the second period T2 longer than the first period T1, thecontroller (not illustrated) determines that the attached developercartridge 8 is a standard type.

When the distal end portion 14 is separated from the outercircumferential wall 302A of the second protrusion 302, the lever 10pivots from the detection position to the non-detection position asillustrated in FIGS. 13A and 13B. During the transition from the stateshown in FIGS. 12A and 12B to the state shown in FIGS. 13A and 13B, thetoothed gear portion 332 of the detection gear 300 is separated from thetransmission gear 400. In other words, the sixth end A6 of the toothedgear portion 332 is disengaged from the transmission gear 400 after thesixth end A6 engages the transmission gear 400.

When the toothed gear portion 332 is disengaged from the transmissiongear 400 in this way, the torsion spring 500 (see FIG. 14) urges thedetection gear 300 downstream in the rotation direction, causing thedetection gear 300 to rotate further. This rotation of the detectiongear 300 is stopped when the projection 340 abuts against therestricting portion 210. The detection gear 300 is thus maintained atthe second position.

When the detection gear 300 is maintained at the second position, thetoothless portion 331 faces the transmission gear 400. In other words,in the second position, the toothed gear portion 332 is disposed outsidea rotational locus defined by the gear teeth of the transmission gear400. When the toothless portion 331 faces the transmission gear 400,transmission of the driving force from the transmission gear 400 to thedetection gear 300 is interrupted.

Incidentally, the detection gear 300 is maintained at the secondposition once the developer cartridge 8 is used. If a used developercartridge 8 is attached to the main body of the image-forming apparatusand a printing operation is initiated, the driving force is nottransmitted to the detection gear 300 that is kept at the secondposition. Accordingly, the optical sensor remains in the OFF state evenafter a prescribed period of time has elapsed since the printingoperation is started. The controller then determines that the attacheddeveloper cartridge 8 is old (the developer cartridge 8 is used once ormore).

A relationship between the torsion spring 500 and the spring engagingportion 350 will be described below in detail.

When the detection gear 300 is located at the first position, the firstarm 510 of the torsion spring 500 engages with the first engagingportion 351 of the detection gear 300 to urge the detection gear 300downstream in the rotation direction (see FIG. 14). At this time, sincethe toothed gear portion 332 of the detection gear 300 engages with thetransmission gear 400, this engagement prevents the detection gear 300from rotating by the urging force of the torsion spring 500.

When the driving force is transmitted from the transmission gear 400 tothe detection gear 300 to rotate the detection gear 300 in the clockwisedirection in the drawing, the first arm 510 of the torsion spring 500sequentially comes in sliding contact with the second engaging portion352, the third engaging portion 353, the fourth engaging portion 354,and the fifth engaging portion 355. After the first arm 510 of thetorsion spring 500 moves over a tip of the V-shaped convex portionformed by the fifth engaging portion 355 and the sixth engaging portion356 and past the same, the toothed gear portion 332 is disengaged fromthe transmission gear 400 and the first arm 510 then urges the sixthengaging portion 356 in the clockwise direction in the drawing.

The detection gear 300 is thus rotated by the urging force of thetorsion spring 500. When the projection 340 comes in contact with therestricting portion 210 as illustrated in FIG. 15, the rotation of thedetection gear 300 is halted and the detection gear 300 is located atthe second position. At the second position, the first arm 510 of thetorsion spring 500 is disposed upstream of the sixth engaging portion356 in the rotation direction and the restricting portion 210 isdisposed downstream of the projection 340 in the rotation direction.Accordingly, the detection gear 300 is no longer allowed to rotateupstream or downstream in the rotation direction and is thus maintainedat the second position.

FIG. 16 illustrates a detection gear H1 which is used for the developercartridge 8 of a first high-capacity-type which can accommodate a firstamount of developer that is larger than the amount of developer that thedepicted standard-type developer cartridge 8 can accommodate therein.The detection gear H1 or other types of detection gears H2 and H3 (seeFIGS. 17 and 18), which will be described later, respectively havegenerally the same structures as that of the depicted standard-typedetection gear 300. Accordingly, the same reference numerals will beused for the substantially same configurations as those of the standardtype, and descriptions therefor will be omitted. In the otherhigh-capacity-types of the developer cartridges 8 other than thestandard type, the detection gear 300 of the standard type is replacedwith the detection gears H1, H2 and H3, respectively.

Hereinafter, the structures of the detection gears H1, H2 and H3 will bedescribed.

Referring to FIG. 16, the detection gear H1 integrally includes: thefirst protrusion 301, the shaft portion 310, the disc-shaped portion320, the toothless gear portion 330, the projection 340 and the springengaging portion 350 (not shown in FIG. 16) that are generally the samestructure as those of the detection gear 300 of the standard type; and asecond protrusion 302H1 that is different from the second protrusion 302of the standard-type detection gear 300. The second protrusion 302H1includes the first extension wall 302B, and an outer circumferentialwall 302D. The first extension wall 302B has substantially the sameconfiguration as the first extension wall 302B of the standard type. Theouter circumferential wall 302D has a length in the rotation directionthat is smaller than that of the outer circumferential wall 302A of thestandard-type detection gear 300. That is, in the detection gear H1, theouter circumferential wall 302D has the third end A3 and the fourth endA4 opposite each other in the rotation direction. More specifically, asillustrated in FIG. 19A, an angle about the second axis CL2 between thesecond end A2 of the first protrusion 301 and the third end A3 of thesecond protrusion 302H1 is defined as the third angle θ3, as in thestandard-type detection gear 300. An angle θ1 about the second axis CL2between the third end A3 of the second protrusion 302H1 and the fourthend A4 of the second protrusion 302H1 is set to be the same as the firstangle θ1.

By configuring the detection gear H1 as above, the detection period forthe first time and the non-detection period for the first time both canbe made the same as the first period T1, as in the standard typedetection gear 300. Further, the detection period for the second timecan be set to the first period T1 which is shorter than the detectiontime for the second time in the standard-type detection gear 300 (secondperiod T2), as illustrated in FIG. 20. Accordingly, the controllerdetermines that the mounted developer cartridge is the firsthigh-capacity-type developer cartridge 8 when the detection period forthe second time is detected to be the first period T1.

FIG. 17 illustrates the detection gear H2 which is used for thedeveloper cartridge 8 of a second high-capacity-type that canaccommodate a second amount of developer that is larger than the firstamount of developer that the first high-capacity-type developercartridge 8 can store therein. The detection gear H2 has substantiallythe same configuration as the detection gear H1 for the firsthigh-capacity-type. However, the detection gear H2 includes a secondprotrusion 302H2 that is different from the second protrusion 302H1 ofthe detection gear H1. Specifically, a gap between the second end A2 ofthe first protrusion 301 and the third end A3 of the second protrusion302H2 in detection gear H2 is larger than the gap between the second endA2 of the first protrusion 301 and the third end A3 of the secondprotrusion 302H1 in the detection gear H1.

Specifically, as illustrated in FIG. 19B, an angle θ4 about the secondaxis CL2 between the second end A2 of the first protrusion 301 and thethird end A3 of the second protrusion 302H2 is set to 149° in theembodiment.

By configuring the detection gear H2 as above, as illustrated in FIG.20, the detection periods for the first time and the second time can bemade identical to the first period T1, as in the standard-type detectiongear 300; and the non-detection period for the first time can be set toa third period T3 which is longer than the first period T1. Accordingly,the controller determines that the mounted developer cartridge is thesecond high-capacity-type developer cartridge 8, when the non-detectionperiod for the first time is determined to be the third period T3.

FIG. 18 illustrates the detection gear H3 which is used for thedeveloper cartridge 8 of a third high-capacity-type that can accommodatea third amount of developer that is larger than the second amount ofdeveloper for the second high-capacity-type developer cartridge 8. Thedetection gear H3 includes a third protrusion 303, in addition to thestructure the same as that of the detection gear H1.

The third protrusion 303 is arranged upstream of the second protrusion302H1 in the rotation direction. In other words, the second protrusion302H1 is disposed between the first protrusion 301 and the thirdprotrusion 303.

The third protrusion 303 includes an outer circumferential wall 303A andan extension wall 303B. The outer circumferential wall 303A protrudes inthe axial direction from the disc-shaped portion 320 and hassubstantially the same configuration as the arcuate wall 301A of thefirst protrusion 301. The extension wall 303B has substantially the sameconfiguration as the extension wall 301B of the first protrusion 301.The outer circumferential wall 303A has a seventh end A7 constitutes adownstream end in the rotation direction and an eighth end A8 whichconstitutes an upstream end in the rotation direction. The eighth end A8is located opposite the seventh end A7, and is separated farther awayfrom the second protrusion 302H1 than the seventh end A7 is from thesecond protrusion 302H1.

As illustrated in FIG. 19C, an angle about the second axis CL2 betweenthe seventh end A7 of the third protrusion 303 and the eighth end A8 ofthe third protrusion 303 is set to be equal to the first angle θ1 aboutthe second axis CL2 between the first end A1 of the first protrusion 301and the second end A2 of the first protrusion 301.

As illustrated in FIG. 19C, an angle about the second axis CL2 betweenthe fourth end A4 of the second protrusion 302H1 and the seventh end A7of the third protrusion 303 is set to be the same as the third angle θ3about the second axis CL2 between the second end A2 of the firstprotrusion 301 and the third end A3 of the second protrusion 302H1. Adistance from the seventh end A7 to the eighth end A8 is set to be thesame as the distance D1 that is the distance from the first end A1 tothe second end A2, more specifically, within a range from 3.0 mm to 6.0mm.

By configuring the detection gear H3 as above, the optical sensor can bemade ON three times while the detection gear H3 rotates from the firstposition to the second position, as illustrated in FIG. 20. Accordingly,the controller determines that the mounted developer cartridge is thethird high-capacity-type developer cartridge 8 when the optical sensoris rendered ON three times. In the third high-capacity-type developercartridge 8, the detection periods from the first to third times and thenon-detection periods for the first and second times are respectivelyset to be the first period T1 as in the standard-type detection gear300.

According to the above-mentioned configurations, the followingoperational and technical advantages can be achieved.

By so configuring the first angle θ1 which is an angle about the secondaxis CL2 between the first end A1 and the second end A2 to be within arange from 15° to 21°, the period of time in which the lever 10 issupported by the first protrusion 301 can be extended, which can makethe detection period longer if compared to a conventional art. Bysetting the third angle θ3 which is an angle about the second axis CL2between the second end A2 and the third end A3 to be within a range from62° to 69°, the period of time in which the lever 10 is located betweenthe first protrusion 301 and the second protrusion 302 can be madelonger, and the non-detection period can also be set to longer thanever, just like the detection period.

Various variations and modifications are conceivable.

The shape of the detection gear 300 is not limited to theabove-mentioned embodiment and may be appropriately modified intovarious shapes. Here, for example, assume a configuration that: adeveloper cartridge 8M according to a modification to the embodiment maybe supported by a drawer such that the developer cartridge 8M ispivotable about the axis of the developing roller 81; and the developercartridge 8M may be configured to be in a first posture during aprinting operation and then pivot into a second posture from the firstposture when the developer cartridge 8M is detached from the drawer. Inthis case, when the developer cartridge 8M is pivoted from the firstposture corresponding to FIG. 13A to the second posture corresponding toin FIG. 21, for example, the second protrusion 302 of the detection gear300 may be located to overlap with the distal end portion 14 of thelever 10 when viewed in a detachment direction of the developercartridge 8M. In this case, when the developer cartridge 8M is detachedfrom the drawer in the detachment direction, the second protrusion 302may get stuck with the distal end portion 14 of the lever 10, making thedetachment of the developer cartridge 8M difficult. This problem occursnot only in the standard type detection gear 300, but also in the othertypes of detection gears H2 and H3 in which another protrusion (secondprotrusion 302H2 and third protrusion 303) is positioned opposite to thefirst protrusion 301 with respect to the second axis CL2.

In order to solve this problem, the detection gears 300, H2, and H3 maybe formed in shapes as shown in as illustrated in FIGS. 22A through 24B,for example. Specifically, FIGS. 22A and 22B show a standard-typedetection gear 300M according to the modification provided in thedeveloper cartridge 8M. This detection gear 300M includes a secondprotrusion 302M that has a cam surface F1 for pushing and lifting thedistal end portion 14 of the lever 10 up to the position correspondingto the detection position (i.e., in a direction intersecting thedetachment direction) at the time of detachment of the developercartridge 8. In the second posture of the developer cartridge 8M (shownin FIG. 22A), the cam surface F1 and the distal end portion 14 arearranged such that: an upstream end F11 of the cam surface F1 in thedetaching direction is disposed closer to the position corresponding tothe detection position than a tip face 14A of the distal end portion 14is; and the upstream end F11 is positioned upstream relative to the tipface 14A in the detachment direction.

The cam surface F1 is inclined with respect to the detachment directionwhen the developer cartridge 8 is in the second posture (shown in FIG.22A). Specifically, when the developer cartridge 8 is in the secondposture, the cam surface F1 obliquely extends, from the upstream endF11, in a prescribed direction from the position downstream in thedetachment direction and corresponding to the detection position towardthe position corresponding to the non-detection position, to a positionwhere a downstream end F12 of the cam surface F1 is disposed downstreamrelative to the tip face 14A of the lever 14 in the prescribed directionfrom the position corresponding to the detection position to theposition corresponding to the non-detection position.

FIGS. 23A and 23B show a second high-capacity-type detection gear H2Maccording to the modification. The second high-capacity-type detectiongear H2M may also be provided in the developer cartridge 8M. The secondhigh-capacity-type detection gear H2M includes a second protrusion 302M2provided with the cam surface F1 that is substantially the same as thecam surface F1 in the standard-type detection gear 300M. Specifically,in the cam surface F1, an upstream end F11 thereof in the detachmentdirection is disposed at a position closer to the position correspondingto the detection position than the tip face 14A of the distal endportion 14 of the lever 10 and upstream of the same in the detachmentdirection, when the developer cartridge 8 is in the second posture.

The cam surface F1 is inclined with respect to the detachment directionwhen the developer cartridge 8 is in the second posture. Specifically,when the developer cartridge 8 is in the second posture, the cam surfaceF1 obliquely extends, from the upstream end F11, in the prescribeddirection (from the position downstream in the detachment direction andcorresponding to the detection position toward the positioncorresponding to the non-detection position) to the position where thedownstream end F12 is disposed downstream relative to the tip face 14Aof the distal end portion 14 in the prescribed direction.

FIGS. 24A and 24B show a third protrusion 303M of a thirdhigh-capacity-type detection gear H3M according to the modification thatmay also be provided in the developer cartridge 8M. The third protrusion303M is provided with the cam surface F1 which is substantially the sameas the cam surface F1 in the standard type detection gear 300M.Specifically, in the cam surface F1, the upstream end F11 in thedetachment direction is disposed closer to the position corresponding tothe detection position than the tip face 14A of the distal end portion14 of the lever 10 is, and upstream relative to the tip face 14A in thedetachment direction, when the developer cartridge 8 is in the secondposture.

The cam surface F1 is inclined with respect to the detachment directionwhen the developer cartridge 8 is in the second posture. Specifically,when the developer cartridge 8 is in the second posture, the cam surfaceF1 obliquely extends, from the upstream end F11, in the prescribeddirection from the position downstream in the detachment direction andcorresponding to the detection position toward the positioncorresponding to the non-detection position, to the position where thedownstream end F12 is disposed downstream relative to the tip face 14Ain the prescribed direction.

By configuring the detection gears 300M, H2M, and H3M as describedabove, the following operational and technical advantages can beachieved. Note that, in the following description, the thirdhigh-capacity-type detection gear H3M will be used as a representativeexample to describe the operational technical advantages according tothe modification.

When the developer cartridge 8M is pivoted from the first postureillustrated in FIG. 25 to the second posture illustrated in FIG. 26, theupstream end F11 of the cam surface F1 in the third protrusion 303Mcomes to a location upstream relative to the distal end portion 14 ofthe lever 10 in the detachment direction. When the developer cartridge8M is detached from the second posture in the detachment directionindicated by an arrow show in FIG. 26, the distal end portion 14 of thelever 10 is moved along the cam surface F1 while being pushed up by thesame up to the position corresponding to the detection position, asillustrated in FIG. 27. The developer cartridge 8H can be detached withease.

As a further variation, instead of the toothed gear portion 332 of thedepicted embodiment, a frictional member may be employed as theengagement portion, for example. This frictional member may beconfigured to frictionally engage with the transmission gear 400. Forexample, rubber can be used as the frictional member.

Further, while the torsion spring 500 is used as the spring in theabove-mentioned embodiment, the present disclosure is not limited tothis configuration. For example, a coil spring, a leaf spring, or aresin having resiliency may be used as the spring.

Further, the laser printer 1 is exemplified as the image-formingapparatus according to the present disclosure in the depictedembodiment, but the disclosure may be applied to other image-formingapparatuses, such as a copying machine and a multifunction device.

In the above-mentioned embodiment, the disclosure is applied to thedeveloper cartridge 8 including the developing roller 81 and thedeveloper container 84. However, the disclosure is not limited to thisexample. For example, if a developing device including a developingroller and a developer cartridge including a developer container areconfigured as separate components, the disclosure may be applied to thedeveloper cartridge.

In the above-mentioned embodiment, the protrusions 301, 302, 303 areformed integrally with the detection gears 300, H1, H2 and H3. However,the disclosure is not limited to this configuration. For example, theprotrusions may be separately provided from the detection gears, and maybe formed of, for example, a resin film or a plate-like rubber material.

In the above-mentioned embodiment, the shaft portion 310 is hollow, butthe shaft portion may be formed to be solid, instead.

The detection gear 300 (H1, H2, H3) is configured to engage with thetransmission gear 400 supported by the agitator 85 in the embodiment,but the detection gear 300 (H1, H2, H3) may be configured to engage withthe idle gear 140 rather than the transmission gear 400.

While the disclosure is described in detail with reference to thespecific embodiments thereof while referring to accompanying drawings,it would be apparent to those skilled in the art that many modificationsand variations may be made therein without departing from the scope ofthe disclosure.

What is claimed is:
 1. A developer cartridge comprising: a first gearconfigured to rotate about a first axis extending in an axial direction,the first gear including gear teeth; and a second gear configured torotate in a rotation direction about a second axis extending in theaxial direction, the second gear having a peripheral surface extendingin the rotation direction, the second gear comprising: an engagementportion formed on a part of the peripheral surface and extending in therotation direction, the engagement portion being configured to engagethe gear teeth; a first protrusion protruding in the axial direction andextending in the rotation direction, the first protrusion having a firstend and a second end opposite to each other in the rotation direction;and a second protrusion protruding in the axial direction and extendingin the rotation direction, the first protrusion and the secondprotrusion being configured to move together with the engagementportion, the first protrusion and the second protrusion being arrangedto be spaced apart from each other in the rotation direction, the secondend being arranged closer to the second protrusion than the first end isto the second protrusion, the second protrusion having a third end and afourth end opposite to each other in the rotation direction, the fourthend being arranged farther away from the first protrusion than the thirdend is from the first protrusion, the first end and the second enddefining a first angle therebetween about the second axis, the secondend and the third end defining a second angle therebetween about thesecond axis, the first angle being smaller than the second angle.
 2. Thedeveloper cartridge as claimed in claim 1, wherein the first angle isnot less than 15° but not more than 21°, and wherein the second angle isnot less than 62° but not more than 69°.
 3. The developer cartridge asclaimed in claim 1, wherein the third end and the fourth end define athird angle therebetween about the second axis, the third angle beinglarger than the second angle.
 4. The developer cartridge as claimed inclaim 3, wherein a sum of the first angle, the second angle and thethird angle is larger than 180°.
 5. The developer cartridge as claimedin claim 1, further comprising: a casing configured to accommodatedeveloper therein; and an agitator configured to agitate the developerwithin the casing, the first gear being supported by the agitator. 6.The developer cartridge as claimed in claim 5, wherein the second gearfurther comprises a disc-shaped portion centered on the second axis, thedisc-shaped portion having an opposing surface opposing the casing andanother surface opposite the opposing surface, the disc-shaped portionhaving a peripheral surface connecting the opposing surface and theanother surface, the first protrusion and the second protrusionprotruding from the another surface, the engagement portion beingprovided along the peripheral surface of the disc-shaped portion.
 7. Thedeveloper cartridge as claimed in claim 6, further comprising a springin contact with the second gear, wherein the second gear furthercomprises a spring engaging portion protruding from the opposing surfaceof the disc-shaped portion toward the casing, the spring engagingportion being in engagement with the spring, the spring engaging portionhaving a length in the axial direction that is larger than a length ofthe engagement portion in the axial direction.
 8. The developercartridge as claimed in claim 6, wherein the engagement portion has afifth end and a sixth end opposite each other in the rotation direction,the fifth end being engageable with the gear teeth of the first gear, adirection from the fifth end toward the sixth end along the engagementportion being defined as a first direction, the fifth end and the secondend defining a length therebetween in the first direction that isshorter than a length defined between the fifth end and the third end inthe first direction.
 9. The developer cartridge as claimed in claim 8,wherein the second gear is configured to move from a first position to asecond position, the fifth end of the engagement portion being incontact with the gear teeth of the first gear when the second gear is atthe first position, the sixth end of the engagement portion contactingthe gear teeth while the second gear moving from the first positiontoward the second position, the gear teeth defining a rotational locusin accordance with rotation of the first gear, the sixth end of theengagement portion being located outside the rotational locus of thegear teeth when the second gear is at the second position.
 10. Thedeveloper cartridge as claimed in claim 9, further comprising a gearcover configured to cover the first gear and a part of the second gear,wherein the second gear further comprises a projection protrudingradially outward from the peripheral surface of the disc-shaped portion,the projection being configured to contact the gear cover when thesecond gear is at the second position, the projection and the casingdefining a distance therebetween in the axial direction that is largerthan a distance defined between the engagement portion and the casing inthe axial direction.
 11. The developer cartridge as claimed in claim 1,wherein the second protrusion has a length in the rotation directionthat is larger than a length of the first protrusion in the rotationdirection.
 12. The developer cartridge as claimed in claim 1, whereinthe second gear comprises a third protrusion protruding in the axialdirection and extending in the rotation direction, the second protrusionbeing arranged between the first protrusion and the third protrusion,the third protrusion having a seventh end and an eighth end opposite toeach other in the rotation direction, the eighth end being arrangedfarther away from the second protrusion than the seventh end is from thesecond protrusion, the fourth end and the seventh end defining an angletherebetween that is not less than 62° but not more than 69° about thesecond axis, the seventh end and the eighth end defining an angletherebetween that is not less than 15° but not more than 21° about thesecond axis.
 13. The developer cartridge as claimed in claim 12, whereinthe seventh end and the eighth end define a distance therebetween thatis not less than 3.0 mm but not more than 6.0 mm.
 14. The developercartridge as claimed in claim 13, wherein the distance defined betweenthe seventh end and the eighth end is not less than 3.8 mm but not morethan 4.5 mm.
 15. The developer cartridge as claimed in claim 1, whereinthe engagement portion comprises gear teeth.
 16. The developer cartridgeas claimed in claim 1, wherein the engagement portion comprises afriction member.
 17. The developer cartridge as claimed in claim 16,wherein the friction member is rubber.
 18. The developer cartridge asclaimed in claim 1, wherein the first end and the second end define adistance therebetween that is not less than 3.0 mm but not more than 6.0mm.
 19. The developer cartridge as claimed in claim 18, wherein thedistance defined between the first end and the second end is not lessthan 3.8 mm but not more than 4.5 mm.
 20. The developer cartridge asclaimed in claim 1, wherein the angle defined between the first end andthe second end about the second axis is not less than 17° but not morethan 20°, the angle defined between the second end and the third endabout the second axis being not less than 63° but not more than 66°. 21.The developer cartridge as claimed in claim 1, further comprising arotatable developing roller extending in the axial direction.